1. Field of the Invention
The present invention relates to a photoelectric conversion film having sharp spectral characteristics, a photoelectric conversion device and a solid-state image pickup device having such photoelectric conversion film and a method of applying an electric field to such devices.
2. Description of the Related Art
A photoelectric conversion film is widely utilized for example in a photosensor, and is particularly advantageously employed as a solid-state image pickup device (photosensor) of an image pickup apparatus (solid-state image pickup apparatus) such as a television camera. The photoelectric conversion film employed as a solid-state image pickup device of the image pickup apparatus is principally constituted of an inorganic material such as a Si film or an a-Si film.
Photoelectric conversion characteristics of a prior photoelectric conversion film utilizing a film of such inorganic material do not have a steep dependence on wavelength. For this reason, an image pickup apparatus utilizing such inorganic material in the photoelectric conversion film generally has a three-plate structure, including a prism for separating an incident light into three primary colors of red, green and blue, and three photoelectric conversion films positioned behind such prism.
However, the image pickup apparatus of such three-plate structure inevitably becomes large in dimension and weight, because of its structure.
In order to realize a compact and light image pickup apparatus, there is desired a single-plate structure utilizing a single photosensor device without a color-separating prism, and an image pickup apparatus of a structure having red, green and blue filters on a single-plate photosensor device is already commercialized and utilized popularly. However, because filters of red, green and blue colors and microlenses for increasing the light concentrating efficiency are laminated, such photosensor device is complex in structure and the efficiency of utilizing of light is not high. For dispensing with the filters, there can be conceived a device provided with photoelectric conversion films having spectral characteristics of red, green and blue colors, and a photoelectric conversion film utilizing an organic material is advantageous in a freedom in designing the light absorbing characteristics.
A photoelectric conversion film utilizing an organic material is represented for example by an electrophotographic photosensitive member and a solar cell, and various materials are being investigated. The material for electrophotography is described for example in Koch and Yee Law, Chemical Rev., 93, 449(1993) while the material for a solar cell is described for example in S. R. Forrest, J. Appl. Phys., 93, 3693(2003), but such materials, having a broad absorption spectrum in a film, result in a broad photoelectric conversion spectrum showing the wavelength dependence of the photoelectric conversion ability, and do not have a sharp wavelength dependence enabling a color separation into red, green and blue colors. Also S. R. Forrest, J. Appl. Phys., 93, 3693(2003) describes an insertion of a BCP intermediate layer between a photoelectric conversion layer and a metal electrode thereby improving a device efficiency, but a device utilizing BCP is insufficient in durability.
A photosensor device utilizing an organic film capable of color separation into red, green and blue colors is described, for example, JP-T No. 2002-502120, JP-A Nos. 2003-158254 and 2003-234460, and S. Aihara, Appl. Phys. Lett., 82, 511 (2003). For example the JP-A No. 2003-234460 describes, in an example, a coumarin 6/polysilane film having a photosensitivity in the entire blue region of 500 nm or less, and a rhodamine 6G/polysilane film having a photosensitivity in the green region, but both elements have an internal quantum efficiency of photoelectric conversion as low as 1%, and are also insufficient in durability. Also a device utilizing a ZnPc/Alq3 film as a photoelectric conversion film has a relatively high internal quantum efficiency of about 20%, but is insufficient in the spectral characteristics, having an absorption in the blue color region in addition to the red color region. Thus, such films are insufficient in the spectral characteristics, light-emitting characteristics and device durability for use as an image pickup device, and improvements are being desired. Also the use of quinacridone as a photoelectric conversion material is described in JP-A No. 2004-134933, but is merely mentioned as an example of organic pigments, and no description is made on the method of use capable of satisfying the spectral characteristics, light-emitting characteristics and device durability.